Automatic controls for
street lighting have been available since the days of gas lighting - however,
manual switching was still very much the norm for many years due to the
automatic controls proving expensive. Lamplighters were employed to go to every
lantern in a given area at dusk and activate the gas supply. Most required the
lamplighter to go up to the lantern (hence the need for ladder bars on the
columns) and light the mantles that way. The lamplighter would then return at
dawn and turn the lanterns off again.

The first big change came
when a time switch was developed which switched the gas supply on/off
automatically. These worked on clockwork and needed to be wound up every few
days in order to keep accurate timing. Where gas lighting is employed today,
this method is often still used to switch the lanterns on or off. An alternative
method these days is to have the gas supply regulated electronically with valves
controlled by a photocell.

With the increase in
popularity of electric lighting, manual switching again became popular - many
lantern companies made their own switches which would fit between the column and
the bracket. They were often designed in such a way that the lamplighter could
remain on the ground - a long stick with a hook on the end could be used to
flick the switch and turn the lantern on or off.

Time switch operation
again soon took over with the invention of the 'solar dial' - a device which
could automatically change its on and off times depending on the time of year -
determined by a date wheel on the dial. The solar time switch quickly became the
standard method of controlling lighting loads. Not all units ran the standard
dusk-dawn operation - units were developed which allowed for the load to be
deactivated at a given time every night (for example, midnight) and then
reactivate in the early morning. Other variants included 'dual circuit' time
switches - these catered for lanterns designed to run two (or more) lamps. Both
circuits would activate at dusk but then one would work part-night, switching
off one of the lamps in the hours when traffic flows were less. A problem with
some time switch units was that the timing could be 'knocked out' due to power
cuts - causing the lanterns to be in use when they were not required and off
when they were! Certain units later employed a spring reserve in the mechanism
which allowed the dial to continue to turn in the event of a power loss. The
reserve typically lasted for several hours - once power was restored, it would
immediately start being re-wound by the synchronous motor of the time switch via
a slipping clutch.

The popularity of time
switches began to diminish in the 1970s when lighting sensors (photocells) were
increasing in popularity - such products had been around since just after the
Second World War but they were large and, in many cases, unreliable. As
electronics improved, photocells could be made smaller - eventually becoming
about 76 mm (three inches) in diameter, which is also the standard diameter for 5
and 6 m columns. The popularity of photocells was down to the fact that they
required a lot less setting up than a time switch required - if any. The
photocells from the 1970s frequently relied on a thermal relay and Cadmium
Sulphide detector but it wasn't long before all-electronic photocells were
available. The part-nightly option was also available, but the dual-circuit was
never an option. At this time, many dual-lamp lanterns had already been replaced
by single-lamp lanterns so this was not really a problem.

Nowadays, photocell
technology has come on a long way and the switching accuracy has greatly
improved since the early days. Certain photocells can now dim lanterns during
the early hours of the morning in an attempt to save energy. Special control
gear must be provided in order for this to happen however.

Despite this, time
switches are not completely confined to history just yet - certain circumstances
mean that photocells cannot be used - this is often due to the higher switching
capacity of a time switch in comparison to a photocell. Solar-dial time switches
are still made to this day - although the spring reserve has now been replaced
with a battery back-up system. Some digital time switches can also mimic the
operations of a solar-dial nowadays - these are often sold with a 'fit and
forget' tagline.